A YIELDING TYPE HYDRAULIC PROP USEFUL FOR SUPPORTING MINE ROOFS

Abstract

A yielding type hydraulic prop useful for supporting mine roofs which comprises a pressure cylinder (18), housing an inner tube (23) having at the top end a channel (28) and an external guard tube (26) fixed by means (27) and at the bottom end a piston head (22) and pressure seal (19) fixed by mean (20,21), the top of the pressure cylinder being provided with a stopper (24) wiper ring (250 and the bottom being fixed to the top of a connecting block (16), the bottom of the connecting block being fixed to the top of bottom tube (17) having base plate (29), the said connecting block (16) housing by means (7,8) setting valve (14) and release valve (15), the setting valve (14) having means (1,2,3,4,5,30) to provide hydraulic pressure to raise the inner tube (23) and the release valve (15) having means (6,9,10,11,12,13) to provide automatic release of hydraulic pressure for load exceeding rated prop load capacity

Full Text

This invention relates to a yielding type hydraulic prop useful for supporting mine roofs. The prop of present invention is parti-cular/ly useful,for supporting freshly exposed mine roofs of blasting faces.
Every year a number of lives -are lost due to accidents arising from fall of roofs and side walls in mines. A major number of these accidents occur within a zone of 6 metres from the working face under freshly exposed roofs. The falls occur due to the disturbance of natural rock support equilibrium caused by excavation/opening of drivage. To nulify such disturbance of equilibrium, development of appropriate roof support is a must for safe mining operation. It has been experienced that rigid props without adequate setting load are incapable to meet this challange as these get dislodged during blasting operation. Moreover, release of concentrated support load which is in excess of the rated capacity of the support, is an useful requirement and this feature .is not taken into account in case of any rigid type of support.
To the best of our knowledge no hydraulic prop incorporating the essential features like setting load with hand operated mechanism for preventing dislodgement during blasting,yielding characteristics as ptotection towards overloading,safe release from a remote place and lightness for easy handling has been developed.
In the existing type hydraulic prop,the total hydraulic travel required is much more than the developed prop. For this reason a
frighier length of honed seamless tube is required for the ofixt-sting prop? Whereas in case of developed prop only a limiteid travel is sufficient^thus a much less length of honed" seamlees tube is required and the rest length may be adjusted by ordinary tube resulting a much reduction in cost. For setting the existing prop,an electric operator costly power pack is required whereas in the developed prop only a hand operated ordinary hydraulic pump is sufficient for the purpose.
Keeping this in view the development of yielding type hydraulic prop, is useful for supporting freshly exposed roof in blasting faces, has been taken up. The development would help
1) To eliminate the use of Timber and rigid props:
2) To ensure a high and definite setting load; .
3) To provide yielding arrangement to give a clear indication in case of roof load, exceeding the rated capacity of the prop a-nd to protect the damage of the Scheme from over loading: and
4) To achieve quick & easy setting and releasing operation.
The main object of the present invention is to provide a yielding
type hydraulic prop useful for supporting mine roofs. Another
object of the present invention is to provide an improved prop
useful for supporting the freshly exposed roof of a blasting face
covering the advantages of high induced setting load and yielding
characteristics ensuring safety.
Yet Another object is to achieve quick and easy setting/releasing of the prop ensuring economy through less time involvement in setting and releasing operation as compared to those required in existing rigid props, lii addition, economy would also be resulted through repeated use of the item.
The figs. I ,2 ,3 of the accompanying drawings with these specification describes as follows;
Fig. 1: Shows the sectional elevcition of the prop.
Fig. 2: Shows the pump fitted with hose and setting gun.
Fig. 3. Shows the plan cind elevation of release lever.
The various parts depicted in the drawings are-.
Part No. Name of Part
1 . Nozzle.
2. Steel ball
3. Conical spring.
4. Teflon seat.
5. Central valve body.
6. Release valve spring.
7. Neoprene 0' ring.
8. " Neoprene "O'ring.
9. Relief valve adjusting nut.
10. Steel ball.
11. Gui de pi n.
12. Relief valve spring.
13. Valve casing.
14. Left side valve cartridge.
15. Right side valve cartridge.
Accordingly, the present invention provides an improved device useful for eliminating vortex formation during continuous casting of steel, characterized in that providing a circular disc at the downstream of nozzle, the said device comprises a tundish (5) having a ladle (1) for holding molten steel (2) being placed above the tundish, the ladle (1) having a downstream nozzle (3), the molten steel being transferred to the tundish (5) through a submerged downstream nozzle (3), the nozzle (3) at its lower submerged end being provided with a circular disc (4) attached to its outer periphery, the tundish being provided with a plurality of outlets (6) to pass air bubble free liquid steel into the mould.
The device of the present invention helps in eliminating >90% vortex formation at the downstream entry region irrespective of the level of molten steel in the ladle.
The following examples are given by way of illustrations and should not be construed to limit the scope of the present innovation.
Example-1
A tundish of perspex material of size 150 cm length, 83.5 cm width and 57.7 cm height with three sides inclined at 70 and one side inclined at 82 to the horizontal was fabricated and placed on a stable steel frame super structure. On this superstructure a plastic container 50 cm top dia and 40 cm bottom dia with a height of 50 cm was placed. A downstream glass tube of 2 cm dia was connected to the plastic container at the bottom eccentric location. Water was filled in the container to a level of 40 cm and allowed to flow through the downstream tube into the central region of the perspex tundish. Water was replenished in the
The present invention provides a hydraulically operated open circuit prop useful for supporting freshly exposed mine roof of blasting faces which comprises of an inner tube (23) and a pressure cylinder (18), and a bottom tube (17), a connecting block (16), a valve cartridge (14,15), and a guard tube (260. The inner tube (23) can be extended hydraulically like a ram by injecting hydraulic fluid into the pressure cylinder (18) through a setting gun connected with a hand operated pump (Fig.2) and a hose.
The setting valve (1,2,3), releasing valve (4,6,14) and a relief valves (9,10,11,12) are enclosed within the connecting block (16) fitted in between the pressure cylinder (18) and bottom tube (17). The piston head (22) fitted with pressure seal (19) by the retaining plate (20) and screws (21) is welded at the bottom of the inner tube (23).
With the help of a hand operated pump (Fig.2), fitted with hose and setting gun, water oil emulsion is fed into the pressure cylinder (18) through the nozzle (1) of the setting valve (1,2,3,). During pumping, the steel ball (2) is pressed by the pressurised emulsion against the conical spring (3) and the emulsion enters into the pressure cylinder (18) thought eh holes (30) provided in the central valve body (5), valve cartridge (14) and the connecting
block(16). The inner tube(23) is extended hydrauli cally like a ram by the hydraulic pressure induced by the pump(Fig.2). As soon
as the required setting load is achieved, the setting gun is withdrawn from the prop.
When the hydraulic pressure within the pressure cylinder(18), due to roof load, exceeds the limit relevent to the load capacity of the prop, the prop starts yielding automatically maintaining the rated prop load capacity. The high pressure fluid from inside the pressure cylinder( 18) reaches the steel ball(IO) through the hole provided in the relief valve adjusting nut(9) and presses against the relief valve spring (12) enclosing the guide pin(11) and being housed within the valve casing(13). Thus, fluid from the high pressure cylinder(IB) discharges out through the valve casing(13) to the outside of the prop through the hole provided in the valve casing(IS). The capacity of the prop may be increased or decreased by tightening or loosening the relief valve adjusting nut(9). The nozzle(l), the central valve body(5) and the relief valve assembly (9,12) are integrated together. For withdrawal of the prop, the oval shaped releasing lever(Fig.S) is inserted into the hole provided in the valve cartri dge( 15) and turned. This operation pushes the valve casing (13) which in turn pushes the complete integrated valve body resulting in the creation of an opening in between the Teflon seat(4) and inside diametrical projection of the valve cartridge component(14) causing the fluid to flow from inside the high pressure cylinder (18) to outside of the prop and allowing the prop to collapse.
The base plate(29) is welded with the bottom tube(17) and remains in'contact with the floor of the mine.
The wiper ring(2S) prevents dusts to enter into the prop. The guard tube(26), extending or collapsing together with inner tube (23), has been provided to protect the inner tube(23) from any side blows that may occur during blasting operation. The nut and bolt(27) holds the guard tube(26) with the inner tube(23). A stopper (24) is provided at the top of pressure cylinder (IS) for stopping the guard tube (26 J. A channel piece or prop head (28) has been provided at the too of the inner tube(23) for fixation with the mine roof.
Working principle of the present invention is as follows : The prop of the present invention is based on the open circuit principle using a hand operated pump unit to supply hydraulic fluid (water oil emulsion in the ratio of 95%:5%) through a hose pipe. The reguired uniform setting load can easily be achieved with the hand operated pump.
The prop has an inner tube and a pressure cylinder. The inner tube 'can be extended hydraulically like a ram by supplying hydraulic fluid to the prop through a handy setting gun fitted with the hose of the pump. As soon as the hydraulic pressure inside the prop exceeds the figure relevant to the load capacity of the prop, the same starts yielding automatically.
The valves incorporating the setting, release and relief mechanism are placed within the valve cartridge fitted at the bottom
of the pressure cylinder.
When the roof load acts on the inner tube through prop head, the
same pressurises the fluid within the pressure cylinder and this in turn acts on the relier valve, when the relief valve receives
a load impulse higher than the rated load capacity of the prop, the emulsion pressure opens the valve seat against the spring and thereby allowing the emulsion to discharge out from inside the prop through ho 1 e p ro vi de d in t he re1i e f valve.
For withdrawal of the prop, the oval shaped release lever is inserted into the hole provided in the valve cartridge and is turned from a remote place by pulling action of a chain attached to the release lever. During turning operation, the release lever pushes the complete valve body against the spring causing the opening of Teflon valve seat which in turn provides a passage for the hydraulic fluid from inside the prop causing collapse of the same. The main advantages are:
1) Ensure high induced setting load ( adjustable as per requirement)- an essential requirement for the supports used in blasting faces of mines,
2) Saves time involvement of miners required for setting and ut*4* withdrawl operation of prop.
3) Yielding provision ensures release of excess support load and gives an indication of roof load exceeding the rated capacity of the prop.
4) Ease in setting and releasing.
5) Ease in handling and transportation due to light weight.

We Claim:
1. An improved device useful for eliminating vortex formation during continuous casting of steel, Characterized in that said device comprises a circular disc at the downstream of nozzle and a tundish (5) having a ladle (1) for holding molten steel (2) being placed above the tundish, the ladle (1) having a downstream nozzle (3), the nozzle (3) at its lower submerged end being provided with a circular disc (4) attached to its outer periphery, the tundish being provided with a plurality of outlets (6) to pass air bubble free liquid steel into the mould.
2. An improved device useful for eliminating vortex formation during continuous casting of steel substantially as here in described with reference Fig 2 to of the drawings and examples.